Future projects

Abstract

How are planetesimals made from pieces of rock and ice just metres across? Do giant planets really migrate inwards through protoplanetary disks, leaving gaps in their wake? How are terrestrial planets built within habitable zones? Answers to these questions will remain elusive as long as we have practically no direct observations of what actually takes place inside a protoplanetary disk. Since these disks are opaque to visible light we must resort to the infrared and radio domains to pursue such questions. Spatial resolution and sensitivity in those domains are still not sufficiently high to obtain images of disks. In the infrared, instruments working now and in the future with arrays such as the ESO’s Very Large Telescope Interferometer (VLTI) may reveal something of the activity in central regions near stars, but imaging will be very problematical. Radio astronomers are anticipating the completion, within the next decade, of the Atacama Large Millimeter Array (ALMA) — an interferometer consisting of fifty telescopes designed for millimetric and submillimetric surveys. A joint project of Europe, the USA, Canada and Japan, ALMA is currently under construction in the Atacama Desert of northern Chile, at an altitude of 5,000 metres. Uniquely, it will be able to study protoplanetary disks in all their aspects: size, dynamics, chemical composition, temperature, and the nature of their dust. Although ALMA will be unable to’ see’ even giant protoplanets, it ought to be possible for it to image the gaps created in protoplanetary disks by planets orbiting (like the solar system giants) at a few AU from their stars.